Long-Term Recurrence Risk in HR+/HER2− Early Breast Cancer: Evidence from a Canadian Cohort

Breast carcinoma constitutes the most common malignancy and ranks as the second most frequent cause of cancer-associated death among women in Canada. Approximately two-thirds of all occurrences fall under the HR+/HER2 subtype. This real-world evidence investigation was designed to deliver a thorough assessment of treatment sequences and clinical results in Canadian individuals diagnosed with early-stage HR+/HER2− breast carcinoma. This retrospective, longitudinal cohort evaluation included 541 participants from the pan-Canadian cancer patient database, PMT (Personalize My Treatment). The cohort covered individuals having newly identified or relapsed stage II or III HR+/HER2− breast carcinoma between January 1st, 1992, and May 31st, 2022. Descriptive statistics were used to capture treatment sequences, and the Kaplan-Meier method was applied to evaluate clinical outcomes. In the adjuvant setting, the study found that ET was administered to 75.6% of participants, with a notable preference for pairing ET with cytotoxic drugs, particularly in stage III individuals. Furthermore, neoadjuvant intervention, chiefly employing cytotoxic drugs, was more frequent in stage III individuals, and those undergoing neoadjuvant treatment showed a greater likelihood of proceeding with ET as adjuvant therapy. The median duration of adjuvant ET was 4.5 years. In the adjuvant-treated group, recurrence rates increased progressively over time: 13.2% after 2 years, 21.4% after 3 years, 30.3% after 5 years, and culminating at 58.4% after 10 years. The median time to recurrence in the ET-treated group was 7.76 years. OS figures for ET-treated individuals reached 94.6% at 5 years and 78.3% at 10 years. This investigation brings to light the considerable unmet requirement in stage II and stage III breast carcinoma, with 1 out of 3 individuals relapsing after 5 years, and over half relapsing after 10 years despite adjuvant ET alone. This spotlights the demand for more potent and tolerable therapeutic choices to confront disease recurrence across both short- and long-term horizons for eBC HR+/HER2− patients in Canada.